1. Field of Invention
The present invention relates to an atmospheric pressure plasma reactor for the surface modification of materials and, more particularly, to an atmospheric pressure plasma reactor employing two power supplies for enhancing the surface properties of materials.
2. Related Prior Art
Plasma is quasi-neutral gas consisting of ions, electrons, neutral atoms, excited atoms and various free radicals. Compared with typical chemical or other processing methods, plasma treatment is energy-economic, fast, material-economic and environmentally friendly due to its high energy and high activities. Hence, plasma modifications are widely used for manufacturing various products in industry and commercial applications. Accordingly, various low-pressure plasma reactors such as those based on direct current capacitor discharge, radio frequency capacitor discharge, inductively coupled plasma, electron cyclotron resonance, magnetron sputtering and cathode arc have been proposed.
A dielectric barrier discharge plasma reactor includes at least one dielectric barrier inserted between two discharging electrodes drived by alternating current or pulsed high voltage power supplies such as those disclosed in U.S. Pat. Nos. 5,387,842 and 5,414,324. Nevertheless, as a substrate is located in the discharging zone of the plasma reactor, some problems have been encountered in operating the plasma reactor.
Firstly, the substrate could easily be damaged because of the charged particle bombardments in the plasma reactor.
Secondly, the energy of positive ions is not controllable.
Thirdly, the discharging is not uniform in the plasma reactor due to the interferences between substrate and plasma.
Fourthly, the surface of the substrate might be damaged or unevenly processed in filamentary discharge.
Fifthly, adjustable parameters in the plasma operation are rather limited.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.